Sexual response in women is generally classified into four stages: excitement, plateau, orgasm, and resolution. Masters and Johnson, Human Sexual Response (Boston, Mass.: Little, Brown & Co., 1966). With sexual arousal and excitement, vasocongestion and muscular tension increase progressively, primarily in the genitals, and is manifested by increased blood flow, elevated luminal oxygen tension, and vaginal surface lubrication as a result of plasma transudation that saturates the fluid reabsorptive capacity of the vaginal epithelium. Vasoactive intestinal polypeptide ("VIP") release may induce the physiological changes of sexual arousal and excitement, and may be the major neurotransmitter which participates in the innervation of the vaginal blood supply. Peptide histidine methionine has been co-located with VIP within nerve fibers that innervate small blood vessels, smooth muscle and epithelial cells in the vaginal tract.
Sexual excitement is initiated by any of a number of psychogenic or somatogenic stimuli and must be reinforced to result in orgasm. With continued stimulation, excitement progresses in intensity into a plateau stage, from which the individual can shift into orgasm. The orgasmic stage is characterized by a rapid release from vasocongestion and muscular tension.
During the various stages of sexual response, characteristic genital and extragenital responses occur. Estrogens magnify the sexual responses; however, sexual responses may also occur in estrogen-deficient individuals. Sexual dysfunction may be due to organic or functional disturbances. For example, a variety of diseases affecting neurologic function, including diabetes mellitus and multiple sclerosis, may interrupt sexual arousal. More commonly, local pelvic disorders, such as endometriosis and vaginitis, both of which cause dyspareunia (difficult or painful coitus) may also affect a woman's sexual response. In addition, estrogen deficiency, causing vaginal atrophy and dyspareunia, is a common cause of sexual dysfunction. For a discussion of other causes of female sexual dysfunction, see, e.g., Kaplan, The Evaluation of Sexual Disorders: Psychological and Medical Aspects (New York: Brunner-Mazel, 1983), and Kolodny et al., Textbook of Sexual Medicine (Boston, Mass.: Little, Brown & Co., 1979).
Excitement stage dysfunction generally involves touch sensation impairment, loss of clitoral sensation, vaginal dryness and urinary incontinence. Such excitement phase dysfunction generally results in dyspareunia. Dyspareunia is thought to affect approximately 40% of women, due in large part to inadequate lubrication. It has been estimated that over 40 million women will suffer dyspareunia at some time in their lives. On the order of twenty-five million will experience dyspareunia in the peri- and postmenopausal period (see Kelly, S. (1992) Clinical Practice and Sexuality 8(8):2 and Sato et al. (1992) Clinical Practices in Sexuality 8(5):1). Contemporary symptomatic treatments generally involve the use of physiologically safe lubricants such as egg white, K-Y surgical lubrication jelly (hydroxyethylcellulose), Astroglide.RTM., and Replens.RTM.. See: Semmens (1974) Medical Aspects of Human Sex 8:85-86; and Frishmen et al. (1992) Fertility and Sterility 58(3):630. When symptomatic treatment fails, pharmacological treatment may be indicated.
Estrogen therapy is commonly used in the pharmacological treatment of sexual dysfunction in women. Estrogen-based therapies are generally used to increase mucous production, provide vasodilatory effects, or to increase the general health of the vagina. Nadelson et al., eds., Treatment Interventions in Human Sexuality (New York: Plenum Press, 1983). In such treatments, estrogen is administered orally, parenterally (e.g., by injection), or topically. With oral administration, the estrogen concentration encountered by the liver is generally four- to five-fold greater than estrogen levels in peripheral blood (the "first pass effect"). This effect may lead to an undesirable increase in the production of certain coagulation factors and renin substrates by the liver. Parenterally administered estrogen avoids the first pass effect in the liver. However, all estrogen-based therapies are known to increase the risk of endometrial hyperplasia endometrial cancer and breast cancer in treated individuals.
Because of the increased risk of endometrial hyperplasia and endometrial cancer encountered with unopposed estrogen therapies, estrogen/progestogen combinations have been employed. However, progestogens are known to have some androgenic activity. Further, common side effects from such therapies include uterine bleeding and the continuation of menstrual periods. Accordingly, there remains a need in the art to provide safer and more effective treatments of female sexual dysfunction.
The present invention is directed to the aforementioned need in the art, and provides a new, highly effective method of treating sexual dysfunction. The method involves vaginal and/or vulvar administration of a pharmaceutical formulation containing one or more vasodilating agents, e.g., a prostaglandin or the like.
Drug therapy for treating female sexual dysfunction has been described. For example, U.S. Pat. No. 4,507,323 to Stern describes the use of the anxiolytic m-chloro-.alpha.-t-butylamino-propiophenone in the treatment of sexual dysfunction in male and female individuals. Pharmaceutical compositions containing the agent are described, which are presented in discrete units, e.g., cachets, tablets, capsules, ampules and suppositories for oral or anal delivery of the agent.
Additionally, U.S. Pat. No. 4,521,421 to Foreman describes the treatment of sexual dysfunction in male and female individuals using the stereoisomers of octahydropyrimido4,5-g!quinoline agents, centrally acting dopamine agonists.
U.S. Pat. No. 5,190,967 to Riley describes the treatment of sexual disorders in male and female individuals using heterocyclic benzodioxinopyrrole compounds, which, like the drugs described in the aforementioned patents, are centrally acting agents.
A number of references describe various methods and devices suitable for vaginal or uterine drug administration, and may accordingly be of some interest with respect to the present invention. The following are representative of such references:
U.S. Pat. No. 3,967,618 to Zaffaroni describes an intrauterine device adapted for drug delivery. A number of drugs are mentioned as being suitable for use in conjunction with the device. However, the Zaffaroni patent does not mention treatment of sexual dysfunction, nor is application of a drug-containing composition to the clitoris or vulvar area disclosed or suggested. U.S. Pat. No. 3,948,254 to Zaffaroni is a related patent which describes an intrauterine device for continuous administration of a contraceptive agent.
U.S. Pat. No. 4,014,987 to Heller et al. describes a tampon-like device for delivery of a drug to the uterus or vagina. Heller et al. mention that delivery of prostaglandins is a preferred use of the invention; however, there is no disclosure concerning treatment of sexual dysfunction or delivery to the clitoris.
U.S. Pat. No. 4,564,362 to Burnhill describes a vaginal sponge for controlled release of a contraceptive agent.
U.S. Pat. No. 3,800,038 to Rudel describes a method and composition for uterine administration of steroid hormones. Prostaglandins such as PGE.sub.1 are mentioned as useful in conjunction with the invention. However, there is no disclosure concerning vaginal drug delivery, application of a drug-containing formulation to the clitoris or surrounding vulvar area, or treatment of sexual dysfunction.
U.S. Pat. No. 4,961,931 to Wong describes a vaginal drug administration device adapted to deliver contraceptive hormones, including progestational and estrogenic hormones;.
U.S. Pat. No. 4,112,942 to Scaife generally describes vaginal administration of medicinal foams.
The vaginal delivery of prostaglandins in connection with contraceptives, labor and delivery has also been described. U.S. Pat. No. 4,976,692 to Atad describes the uterine administration of a composition containing PGE.sub.2 and triacetin gel in priming the cervix before induction of labor.
Vaginal PGE.sub.2 suppositories ("Prostin E2.RTM.") and a cervical gel containing PGE.sub.2 ("Prepidil".RTM. gel), both manufactured by Upjohn (Kalamazoo, Mich.), are commercially available. See, e.g., Physicians' Desk Reference.RTM., 51st Edition (Montvale, N.J.: Medical Economics Data Production Company, 1997). The suppositories are primarily indicated for evacuation of uterine contents, while the gel is used in connection with induction of labor.
U.S. Pat. Nos. 4,818,517 to Kwee et al., 4,680,312 to Johnson, 4,454,339 to Skaballa et al. and 4,128,577 to Nelson each relate to vaginal administration of prostaglandins. However, the documents generally describe the use of prostaglandins in contraceptives, labor and delivery, and thus fail to disclose or suggest the use of these compounds in the treatment of sexual dysfunction.
U.S. Pat. No. 4,254,145 to Birnbaum is also of interest, and relates to the use of prostaglandins, including natural and synthetic analogues of prostaglandin types PGE, PGA and PGE.sub..beta., in the treatment of arteriospastic and occlusive peripheral vascular disorders as well as in the treatment of impotency. The described methods of treatment involve topical administration or localized injection of pharmaceutical compositions containing the exemplified prostaglandins to increase peripheral circulation. The compositions are also described for use in lowering systemic blood pressure. Although a number of therapeutic applications are described, Birnbaum fails to disclose the treatment of female sexual disorders using vaginal, vulvar or clitoral delivery of prostaglandins.
There are, accordingly, a number of background references relating to treatment of female sexual dysfunction as well as cervical or uterine administration of prostaglandins. However, the present method for treating female sexual dysfunction, by way of vaginal and/or vulvar delivery of a vasodilating agent such as a prostaglandin, is completely novel and unsuggested by the art.